Description
Return inkWidth, leftBearing+inkWidth/2, advance/2, and (leftBearing-rightBearing)/2 as centerOffset.
Typography combines several distinct scales: font size describes an em scale, cap height describes a font metric, leading describes baseline spacing, and variable-font axes select design coordinates. Ratios between them require an explicit convention.
Return inkWidth, leftBearing+inkWidth/2, advance/2, and (leftBearing-rightBearing)/2 as centerOffset.
When to use this tool
Use Glyph Sidebearing Optical Center Offset when you need to compare supplied type metrics or font-axis values on a consistent basis.
How to use the tool and how it works
- Enter advance, leftBearing, rightBearing. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read inkWidth, geometricInkCenter, advanceCenter, centerOffset. Use the output convention below.
Require nonnegative advance and nonnegative advance-leftBearing-rightBearing. Return inkWidth, leftBearing+inkWidth/2, advance/2, and (leftBearing-rightBearing)/2 as centerOffset.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| advance | Advance | Required. Finite number; minimum 0. |
| leftBearing | Left Bearing | Required. Finite number. |
| rightBearing | Right Bearing | Required. Finite number. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| inkWidth | Ink Width | Required. Finite number. |
| geometricInkCenter | Geometric Ink Center | Required. Finite number. |
| advanceCenter | Advance Center | Required. Finite number. |
| centerOffset | Center Offset | Required. Finite number. |
{
"input": {
"advance": 20,
"leftBearing": 2,
"rightBearing": 4
},
"output": {
"inkWidth": 14,
"geometricInkCenter": 9,
"advanceCenter": 10,
"centerOffset": -1
}
}Limitations and assumptions
- Bearings may be signed; the center is a one-dimensional bounding-box midpoint rather than a measured optical center or glyph-shape centroid.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Read actual font metrics and variation tables when available, then proof the text in its intended renderer. A metric calculation cannot replace shaping, glyph inspection, or an actual layout test.
References
Similar or alternative tools
- Optical Margin Supplied Glyph Offset
Return signed outward shifts and subtract both weighted overhangs from glyphAdvance for effectiveWidth.
- Font Axis Default Reference Offset
Subtract suppliedDefault from axisValue and divide by positive suppliedScale for normalizedOffset.